Geoscience Reference
In-Depth Information
VALUES AND TRADE-OFFS
Regardless.of.what.management.decisions.are.made,.there.are.necessary.trade-offs.
among.objectives..For.example,.should.we.manage.for.grassland.or.shrub-associated.
bird.species?.Fire.is.an.important.tool.for.inducing.the.disturbances.needed.to.keep.
some. North. American. ecosystems. healthy,. but. ire. releases. carbon. into. the. atmo-
sphere.. These. trade-offs. link. back. to. the. values. associated. with. the. management.
objectives..We.need.a.process.for.evaluating.these.trade-offs..Evaluating.risks.and.
trade-offs.involves.some.form.of.modeling,.followed.by.review.and.consideration.by.
the.stakeholders.(Williams.et.al..2007;.Gregory.2000;.Gregory.and.Wellman.2001;.
Tompkins.et.al..2008)..Scientiic.information.supports.the.process,.but.the.process.is.
fundamentally.focused.on.values.
Competing.models.of.how.the.system.is.expected.to.respond.to.management.are.
used.to.address.both.uncertainty.and.trade-offs.among.alternatives..A.wide.range.
of.models.are.used.to.support.AM,.including.system.models,.population.models,.
decision.trees,.Bayesian.updating,.and.stochastic.dynamic.programming,.to.name.
a.few.(Walters.1986;.Teeter.et.al..1993;.Kendall.2001;.Nichols.2001;.Nyberg.et.al..
2006;.Starield.and.Bleloch.1991)..The.primary.purpose.for.a.model.in.a.decision-
making. context. is. to. capture. key. relationships. between. alternative. management.
decisions. and. possible. outcomes. (ecosystem. responses),. which. are. tied. directly.
to. the. management. objectives.. Decision. analysts. begin. with. simple. conceptual.
models.and.add.complexity.as.needed.to.address.the.decision.problem—a.process.
referred.to.as.rapid.prototyping.(Starield.et.al..1994)..The.model.plays.a.central.
role.in.both.SDM.and.AM.by.uniting.all.of.the.key.elements.of.the.problem.into.
a.uniied.framework..This.modeling.framework.supports.clear.thinking,.transpar-
ency,.and.can.be.used.to.conduct.sensitivity.analyses.to.assess.which.elements.of.
the. problem. may. have. the. largest. effect. on. the. management. outcomes. (Starield.
and.Bleloch.1991).
EXAMPLE: COASTAL WETLAND IMPOUNDMENTS
AND SEA-LEVEL RISE
We.present.a.case.study.from.the.Refuge.System.that.illustrates.several.components.
of.the.AM.process.described.previously,.as.applied.to.a.climate.change-related.prob-
lem..National.Wildlife.Refuges.in.the.northeastern.United.States.are.using.a.struc-
tured. process. to. help. them. make. decisions. about. whether. to. maintain,. restore,. or.
abandon.freshwater.coastal.impoundments..Generally,.these.freshwater.units.were.
created.by.impounding.a.low-lying.saltmarsh.area..Some.impoundments.may.have.
a. small. freshwater. stream. as. a. water. source,. while. others. are. entirely. dependent.
upon. precipitation.. Freshwater. impoundments. were. originally. created. to. support.
waterfowl. and. other. waterbirds—species. identiied. as. conservation. targets. by. the.
refuges.. As. sea. level. rises. and. the. dikes. that. maintain. these. impoundments. age,.
managers. face. a. costly.decision.about. whether.to. maintain. the. dike,. remove. it,. or.
abandon.it..Maintaining.the.dikes.is.an.example.of.a.“resistance”.strategy.aimed.at.
maintaining.the.status.quo.(Galatowitsch.et.al..2009;.Millar.et.al..2007)..Removing.
the.dikes.and.allowing.the.impoundment.to.revert.to.saltmarsh.is.a.strategy.likely.
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